Segment Information (Details) $ in Thousands |
3 Months Ended | 9 Months Ended | |||||||
|---|---|---|---|---|---|---|---|---|---|
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Sep. 30, 2026
USD ($)
|
Jun. 30, 2026
USD ($)
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Mar. 31, 2026
USD ($)
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Sep. 30, 2025
USD ($)
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Jun. 30, 2025
USD ($)
|
Mar. 31, 2025
USD ($)
|
Sep. 30, 2026
USD ($)
segment
|
Sep. 30, 2025
USD ($)
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Dec. 31, 2025
USD ($)
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| Segment Reporting [Line Items] | |||||||||
| Number of operating segments | segment | 1 | ||||||||
| Number of reportable segments | segment | 1 | ||||||||
| Depreciation and amortization | $ 101,531 | $ 93,424 | |||||||
| Cost of sales | $ 210,563 | $ 209,475 | 624,774 | 592,610 | |||||
| Selling, general and administrative expenses | 8,336 | 7,444 | 23,020 | 21,218 | |||||
| Interest expense—Westlake | 5,110 | 5,947 | 15,314 | 17,391 | |||||
| Net income | 90,857 | $ 82,362 | $ 81,655 | 86,214 | $ 85,795 | $ 42,309 | 254,874 | 214,318 | |
| Assets | 1,225,204 | 1,225,204 | $ 1,256,533 | ||||||
| Operating Segments | OpCo | |||||||||
| Segment Reporting [Line Items] | |||||||||
| Raw material, energy, manufacturing and logistics costs | 178,359 | 175,603 | 523,243 | 499,186 | |||||
| Depreciation and amortization | 32,204 | 33,872 | 101,531 | 93,424 | |||||
| Cost of sales | 210,563 | 209,475 | 624,774 | 592,610 | |||||
| Selling, general and administrative expenses | 7,335 | 6,579 | 20,004 | 18,653 | |||||
| Other segment items | (90) | 175 | 197 | (913) | |||||
| Interest expense—Westlake | 317 | 357 | 945 | 978 | |||||
| Net income | 96,651 | 92,669 | 272,259 | 233,296 | |||||
| Assets | 1,188,150 | 1,188,150 | 1,222,123 | ||||||
| Corporate | |||||||||
| Segment Reporting [Line Items] | |||||||||
| Interest expense—Westlake | 4,793 | 5,590 | 14,369 | 16,413 | |||||
| Net income | (5,794) | $ (6,455) | (17,385) | $ (18,978) | |||||
| Assets | $ 37,054 | $ 37,054 | $ 34,410 | ||||||
| X | ||||||||||
- Definition Amount of asset recognized for present right to economic benefit. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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| X | ||||||||||
- Definition The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Amount of interest expense classified as nonoperating. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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| X | ||||||||||
- Definition Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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| X | ||||||||||
- Definition The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Amount of other expense (income) and loss (gain) calculated as difference between segment revenue and separately disclosed expense category to arrive at segment profit (loss). Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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| X | ||||||||||
- Definition Raw material, energy, manufacturing and logistics costs No definition available.
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- Details
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